Catalytic Conversion of Fructose and 5-Hydroxymethylfurfural into 2,5-Furandicarboxylic Acid over a Recyclable Fe3O4–CoOx Magnetite Nanocatalyst

A nano-Fe3O4–CoOx catalyst was prepared via a simple wet impregnation method. The nano-Fe3O4–CoOx catalyst showed good catalytic performance for the conversion of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid (FDCA) with t-BuOOH as the oxidant. Several important reaction parameters were explored, with the highest FDCA yield of 68.6% obtained from HMF after 15 h at a reaction temperature of 80 °C. One-pot conversion of fructose into FDCA was also successful via two steps. Catalytic conversion of fructose over Fe3O4@SiO2–SO3H yielded 93.1% HMF, which was oxidized in situ into FDCA with a yield of 59.8%. Furthermore, recycling of nano-Fe3O4–CoOx was accomplished with the help of a magnetic field. Nano-Fe3O4–CoOx showed high stability in the reaction process. The use of nonprecious metals and no requirement of a base additive made this method much more economical and environmentally friendly.